The invention relates generally to salient pole synchronous machines and more particularly to rotors of salient pole synchronous machines.
A conventional large salient pole synchronous machine 10 including a stator 12 and a rotor 14 is shown in FIG. 1, and a sectional view of a portion of the rotor is shown in FIG. 2. Examples of conventional salient pole synchronous rotors are shown, for example, in MICHAEL LIWSCHITZ-GARIK and CLYDE C. WHIPPLE, ALTERNATING-CURRENT MACHINES (2d ed. 1961) and RALPH R. LAWRENCE, PRINCIPLES OF ALTERNATING-CURRENT MACHINERY (Henry E. Richards reviser, 4th ed. 1953). In these rotors, end plates 28 typically comprise copper sheets that are shaped to match the profiles of poles 22. Each end plate extends about half-way down the pole and is clamped between supports 32 and 34 which typically comprise shortened steel laminations that permit bending of the end plates and thus allow axial movement of rotor bars 30 (situated in bar holes 26 and electrically coupled to the end plates to form a rotor cage) to accommodate thermal expansion and contraction.
When such machines are driven by electronic converters, considerable harmonic current results in the rotor bars and rotor core and leads to increased heat burdens. During normal operation, because the rotor bar cage is interrupted in the span regions between the poles, rotor bars near pole ends 29 carry more current than the other bars and are more prone to failure. Additionally, harmonic flux penetrates into the rotor core 16, rotor key slots 20, pole keys 24, shaft 18, and rotor windings 17 and creates destructive currents there.
It would therefore be desirable to provide a salient pole synchronous machine rotor with reduced concentration of currents in rotor bars situated near the pole ends. It would additionally be desirable to reduce induction of destructive currents in the rotor core, key slots, pole keys, shaft and windings.
Briefly, in accordance with one embodiment of the present invention, a salient pole synchronous machine rotor comprises a rotor shaft, a plurality of salient poles concentric to the rotor shaft, and end plates facing opposing ends of the salient poles with each end plate extending continuously around the rotor shaft.